Circuit arrangement for all-relay selecting equipment



May 1, 1956 A. MEHLIS CIRCUIT ARRANGEMENT FOR ALL-RELAY SELECTING EQUIPMENT Filed Nov. 16, 1951 Q23 Ow U 25 INVENTOR ARTHUR MEHL IS ATTORNEY nited States Patent CIRCUIT ARRANGEMENT FOR ALL-RELAY SELECTING EQUIPMENT Arthur Mehlis, Stuttgart-Zuifenhausen, Wurttemberg- Baden, Germany, assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application November 16, 1951, Serial No. 256,688

Claims priority, application Germany November 18, 1950 9 Claims. (Cl. 179--18) The invention relates to such selecting equipment for communication systems, in particular telephone systems, as is directed to numerical selection in a certain direction, to select thereafter in non-numerical selection a circuit among those leading in this direction, and which to this end uses relays throughout. Such group selectors are superior to mechanical switches because of the absence of mechanical trouble, and the almost complete absence of wear, and because no vibrations occur while they are directed, and no fritting noise is caused if noblemetal contacts are used.

The invention is based on the probelm of arranging the circuits of selecting equipment of this kind so that not only the switching performance of mechanical switches is duplicated, but even the expenses keep within economically acceptable limits, so the aforementioned merits are not bought by excessive cost.

In accordance with the invention, this problem is solved by providing two groups 01' relays for the numerical and the non-numerical selecting operations of which the one in charge of the numerical selection consists of multicontact relays, which are designed as two-step relays, and which in their successive connection effected by the dialing pulses are energized to perform only their preliminary stroke, while the one multi-contact relay corresponding to the dialed digit is fully energized after the train of pulses has terminated.

The invention is described in the following with the aid of the embodiment shown in the accompanying figure. It shows a circuit arrangement of a four-wire group selector which by a train of pulses is directed to a certain position, and which among the circuits in this direction selects an idle circuit in non-numerical selection. The group selector consists of ten multi-contact relays Z1 Z10 which in the following are termed tens relays, although the invention is not restricted to a decadic layout, and of ten relays E1 to E10 of a second group of relays which in the following are termed units relays, and furthermore of a seizure relay C, a pulse-repeating relay A, a starting relay VP, and two auxiliary relays U and V. The symbols zlvh to z10vh stand for the pre-pull contacts of the tens relays Z1 to Z10 which are operated when these relays pull only through the first part of their stroke because of weak energization. The action is then as follows:

As a group selector is being seized, relay A energizes in the c-wire circuit, via contacts vII and cl, to complete a circuit for relay C via the c-wire, winding of relay C, contact all, and resistor W1. Relay C operates and by means of contact cl interrupts the operating circuit of relay A. Relay A holds on with its windings AH and A111 in the loop circuit via the talking wires a and b. Energization of relay C effects the energization of the auxiliary relay V by means of contact cIlI. Via contact c111 and winding of relay U, an operating circuit for the units relays E1 to E10 is prepared.

After relay V has energized, the capacitor C1 is charged via cIII, C1, vlV, aIV, W3. When the pulse train arrives to direct the group selector to the desired direction, relay A restores pulsewise in accordance with the dialed digit. When the relay falls back for the first time, the capacitor C1 discharges via vlV, alV, Z1(l), so the tens relay Z1 energizes in its pre-stage and closes its pro-pull contact zlvlz. The tens relay Z1 holds itself via the latter contact in the circuit:

plus, cill, zldvlz zlvh, Z161), G11, VP, uV, W4, minus In this circuit the starting relay VP also energizes and with its contact vpl shorts the relay U, but does not start any other action for the time being. When the relay A pulls up the next time, the capacitor C1 is charged anew, and when relay A restores, it discharges via rectifier G12 and relay Z2 (not shown) which pulls up and in turn closes its pre-pull contact z2vh (also not shown). The ectifier Gll prevents the branching off of part of the discharge circuit. By transfer of the pre-pull contact z2vh, the chain locking circuit via the zli'ivh z2vh contacts of relay Z1 is interrupted so it restores.

When the relay A restores and re-energizes for the third time, the same action repeats. Relay Z3 (not shown) thus pulls up and prepares relay Z4, while relay Z2 falls back. This repeats in accordance with the dialed digit, until the last pulse of the train has been received. The tens relay pulling up last then remains energized.

During the train of pulses, the relay V is shorted pulse- Wise via contacts alll, vpVl, but, although it does not fall back then, it restores after the train of pulses has passed and the short-circuit persists for a longer time.

Let us assume, that the digit 1 has been dialed, so that after the pulse train is terminated, the tens relay Z1 is energized fully. The action which effects full energization of relay Z1 will be described below. Relay Z1 is, as mentioned above, a multi-contact relay which in the assumed case has 44- contacts, of which one set of four contacts (zll-zllV) is required for each connected circuit (a-, b-, c-, d-wires), so a total of 40 contacts is provided for 10 circuits in the direction assigned to the tens relay Z1 (for instance, level 1), while the remaining four contacts are used for control purposes, or set aside for purposes of such kind.

Since relay VP holds over for a short time after the tens relay has pulled up fully, all of the units relays E1-E10 are connected via contacts vp (of which only vpll, vplll, vpIV, and vpV are shown), to the outgoing ten test wires c of the selected direction, which wires have been connected-through by the tens relay Z1. Those units relays will pull up which are connected to idle control Wires. Since however, the contacts 21V, (22V, 23V, etc., cut oil the following relays of the chain, the only units relay which remains on, among those which have pulled up, is the foremost one in the chain. Let us assume that relay E1 has pulled up because the first circuit of the selected direction was idle. With its contact elV, relay El cuts off the following relays E2 to E19, bridges the contact vpll with contact 211V, and, by means of its contacts e1- @1111, connects through the control wire a and the talking wires a and b. To prevent, during the starting period, any possible interaction of testing and blocking potentials at the outputs of the relay group cut off by the energizetion of a free-testing units relay (E1 in the example) via those relays (in the example E2 to Bid), rectifier units are provided in series with the contacts vp at the relays E2 to E10.

These testing processes run oil upon termination of the numerical selection in such a short time that they are positively terminated before relay V P falls back. This dropout is effected by a short-circuit by means of contact vV, when relay V upon termination of the numerical selection de-energizes because of a short through the contacts aIII, vpVI. The short-circuit at vV increases the current in the holding circuit of the relay Z1, which extends over the pre-pull contact zlvh, winding Z1(II), and the rectifier Gll, which causes the full pull-up of the relay Z1. Only then can the already-described testing for free circuits take place.

After relay VP has restored, relay U pulls up in the testing circuit. With its contacts uIII and uIV, it cuts the pulse-repeating relay A from the talking wires; with contact 1.1V it introduces the resistor W5 into the holding circuit of relay Z1 to reduce the current flow; and with contact 1411 it removes the ground from relay V. Contact all prevents a short-circuit of relay C.

It may be mentioned in concluding that in parallel to contact vpVI, contacts on the tens relays Z1 to Zltl are arranged, to maintain the short across relay V even after relay VP has restored, before it is brought out of circuit for good by contact 1111.

The release of the switch takes place when the outgoing c-wire loses its potential so relay U restores. The seizure relay C is short-circuited by 111 and all and brings the selector circuit to normal after it has restored.

What is claimed is:

1. In an all-relay switching system for connecting an incoming line with an idle one of the desired numerical groups of outgoing lines, a first group of multi-contact relays, one relay for each group of outgoing lines, a second group of multi-contact relays, one relay for each line of the outgoing groups, means controlled over the incoming line for operating the relay of the first group associated with the desired numerical group of outgoing lines, a test circuit closed thereupon for the winding of a relay of the second group associated with an idle outgoing line in the desired group of outgoing lines, a circuit completed thereupon between the last mentioned line and the incoming line over contacts of the operated relays of the first and second groups, the relays of said first group of relays being two-step relays, the means controlled over the incoming line being responsive to dialing pulses and causing one after the other of the relays of the first group to perform the first step, and means operative upon the performance of the first step by the last relay responding to the final dialing pulse for causing said last relay to perform the second step.

2. In an all-relay switching system for connecting an incoming line with an idle one of the desired numerical groups of outgoing lines, a first group of multi-contact relays, one for each group of outgoing lines, a second group of multi-contact relays, one for each line of the outgoing groups, a starting relay, means controlled over the incoming lines for operating the relay of the desired numerical group, a test circuit closed thereupon for a relay of the second group corresponding to an idle outgoing line in the desired group of outgoing lines, and a circuit completed thereupon between the last-mentioned line and the incoming line over contacts of the operated relays of the first and second groups, the test circuit including the winding of a relay of the second group, a contact of the starting relay, a contact of a relay of the first group, and a test conductor associated with said idle outgoing line.

3. The system, according to claim 2, in which the relays of the first group are two-step relays, further comprising a circuit for operating the starting relay upon the performance of the first step by the first relay of the first group.

4. The system, according to claim 2, in which the relays of the first group are two-step relays, further comprising circuits for maintaining the starting relay operated from the performance of the first step by the first relay in the first group until after the performance of the second step by the last relay to operate in the first group.

5. The system, according to claim 2, in which the test circuit has multiple branches, each branch including a winding of a relay of the second group, said branches being connected to said test circuit in a predetermined order, each branch being connected to the juncture of said test circuit and the next preceding branch through a contact of the relay whose winding is included in said next preceding branch.

6. The system, according to claim 5, further comprising a decoupling rectifier in each branch.

7. The system, according to claim 5, further comprising a locking circuit for each relay of the second group independent of the contact of the starting relay.

8. In an all-relay switching system for connecting an incoming line with an idle one of the desired numerical groups of outgoing lines, a first group of multi-contact two-step relays, one for each group of outgoing lines, a second group of multi-contact relays, one for each line of the outgoing groups, a pulse relay responding to dialing pulses sent over the incoming line, a condenser charged under the control of said pulse relay circuits jointly controlled by the pulse relay for operating the relays of the first group one after the other to perform the first step, means responsive to the last dialing pulse for causing the last operated relay of the first group to perform the second step, a test circuit closed thereupon for a relay of the second group corresponding to an idle outgoing line in the desired group, and a circuit completed thereupon between the last mentioned line and the incoming line over contacts of the operated relays of the first and second groups.

9. The system according to claim 8, in which the test circuit includes all of the windings of the relays of the second group connected in parallel, and means responsive to the operation of one of said relays for disconnecting the others of said relays from the test circuit and thus causing their release.

Saunders Apr. 14, 1942 Bellamy Dec. 14, 1948 

